We are studying the directed migration of cells (chemotaxis). We have defined peptides produced by bacteria that attract phagocytic cells. Now we have isolated and partially characterized materials produced by tumors that are antichemotactic and possible involved in the avoidance of host rejection. These materials are peptides which may represent non toxic antiinflammatory substances. A factor produced by encapsulated tumors is highly chemotactic for fibroblasts and may play a role in the formation of the tumor capsule. Chemoattractants may be involved in a variety of oral facial diseases including inflammatory diseases and oral cancer.